Method and apparatus for transmitting buffer status report for bi-directional transmission in wireless communication system

ABSTRACT

A method and apparatus for transmitting a buffer status report for a bi-directional transmission in a wireless communication system is provided. A user equipment (UE) triggers a buffer status report for the bi-directional transmission, and transmits the buffer status report for the bi-directional transmission or a scheduling request for the bi-directional transmission to a network. The bi-direction transmission may correspond to vehicle-to-everything (V2X) communication.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for transmitting a buffer statusreport for a bi-directional transmission in a wireless communicationsystem.

Related Art

3rd generation partnership project (3GPP) long-term evolution (LTE) is atechnology for enabling high-speed packet communications. Many schemeshave been proposed for the LTE objective including those that aim toreduce user and provider costs, improve service quality, and expand andimprove coverage and system capacity. The 3GPP LTE requires reduced costper bit, increased service availability, flexible use of a frequencyband, a simple structure, an open interface, and adequate powerconsumption of a terminal as an upper-level requirement.

Vehicle-to-everything (V2X) communication is the passing of informationfrom a vehicle to any entity that may affect the vehicle, and viceversa. This information exchange can be used for a host of safety,mobility and environmental applications to include driver assistance andvehicle safety, speed adaptation and warning, emergency response,safety, traveler information, navigation, traffic operations and demandmanagement, personal navigation, commercial fleet planning and paymenttransactions. There is significant societal benefit and commercial valueto delivering safety, mobility and convenience applications that rely onV2X.

V2X applications span a host of media. Basic elements of V2X are thevehicle and its connectivity to any other intelligent transportationsystem (ITS) station. Therefore, V2X includes transceivers located onvehicles, mounted on the roadside infrastructure, in aftermarketdevices, or within handheld devices. V2X communication may occur in someof contexts of vehicle to vehicle (V2V) communication, vehicle toinfrastructure (V2I) communication, vehicle to pedestrian (V2P) (orother vulnerable road users) communication, or vehicle to homecommunication (V2H).

The wide variety of use cases cannot only be met with a short-rangeradio solution working in a peer to peer manner. Some V2X use casesrequire infrastructure assistance for communication, and some use casescan make use of smaller scale infrastructure such as small cells ormethods such as relaying. For this, the 3GPP has a role to play indefining, examining and acting on the variety of use cases to supportthe V2X effort. 3GPP infrastructure and 3GPP proximity-based services(ProSe) can act in support and enhancement to dedicated short rangecommunications (DSRC) to fulfil many use cases. There is also theopportunity for 3GPP to investigate modifications and enhancements toProSe to meet or improve the performance of short range communicationsin terms of spectral efficiency, effective range, bandwidth andthroughput, error resiliency, and improved latency.

Accordingly, various methods for performing V2X communication based on3GPP technology needs to be defined.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for transmitting abuffer status report for a bi-directional transmission in a wirelesscommunication system. The present invention provides a method andapparatus for transmitting a buffer status report used for either uplinkor sidelink for vehicle-to-everything (V2X) communication.

In an aspect, a method for transmitting, by a user equipment (UE), abuffer status report for a bi-directional transmission in a wirelesscommunication system is provided. The method includes triggering abuffer status report for the bi-directional transmission, andtransmitting the buffer status report for the bi-directionaltransmission or a scheduling request for the bi-directional transmissionto a network.

In another aspect, a user equipment (UE) is provided. The UE includes amemory, a transceiver, and a processor coupled to the memory and thetransceiver, and configured to trigger a buffer status report for abi-directional transmission, and control the transceiver to transmit thebuffer status report for the bi-directional transmission or a schedulingrequest for the bi-directional transmission to a network.

A buffer status report or a scheduling request for bi-directionaltransmission can be transmitted effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows LTE system architecture.

FIG. 2 shows a block diagram of architecture of a typical E-UTRAN and atypical EPC.

FIG. 3 shows a block diagram of a user plane protocol stack of an LTEsystem.

FIG. 4 shows a block diagram of a control plane protocol stack of an LTEsystem.

FIG. 5 shows an example of a physical channel structure.

FIG. 6 shows mapping between UL transport channels and UL physicalchannels.

FIG. 7 shows mapping between UL logical channels and UL transportchannels.

FIG. 8 shows mapping between SL transport channels and SL physicalchannels.

FIG. 9 shows mapping between SL logical channels and SL transportchannels for ProSe direct communication.

FIG. 10 shows an example of a scenario of V2X communication.

FIG. 11 shows another example of a scenario of V2X communication.

FIG. 12 shows another example of a scenario of V2X communication.

FIG. 13 shows an example of a bi-directional channel according to anembodiment of the present invention.

FIG. 14 shows another example of a bi-directional channel according toan embodiment of the present invention.

FIG. 15 shows another example of a bi-directional channel according toan embodiment of the present invention.

FIG. 16 shows another example of a bi-directional channel according toan embodiment of the present invention.

FIG. 17 shows a method for configuring a bi-directional channelaccording to an embodiment of the present invention.

FIG. 18 shows a method for transmitting a buffer status report for abi-directional transmission according to an embodiment of the presentinvention.

FIG. 19 shows a method for transmitting data for a bi-directionaltransmission according to an embodiment of the present invention.

FIG. 20 shows a method for performing bi-directional transmissionaccording to an embodiment of the present invention.

FIG. 21 shows a method for performing bi-directional transmissionaccording to another embodiment of the present invention.

FIG. 22 shows a method for performing bi-directional transmissionaccording to another embodiment of the present invention.

FIG. 23 shows a method for performing bi-directional transmissionaccording to another embodiment of the present invention.

FIG. 24 shows a wireless communication system to implement an embodimentof the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The TDMA can be implemented with aradio technology such as global system for mobile communications(GSM)/general packet ratio service (GPRS)/enhanced data rate for GSMevolution (EDGE). The OFDMA can be implemented with a radio technologysuch as institute of electrical and electronics engineers (IEEE) 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), etc.IEEE 802.16m is an evolution of IEEE 802.16e, and provides backwardcompatibility with an IEEE 802.16-based system. The UTRA is a part of auniversal mobile telecommunication system (UMTS). 3rd generationpartnership project (3GPP) long term evolution (LTE) is a part of anevolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA indownlink and uses the SC-FDMA in uplink. LTE-advance (LTE-A) is anevolution of the 3GPP LTE.

For clarity, the following description will focus on the LTE-A. However,technical features of the present invention are not limited thereto.

FIG. 1 shows LTE system architecture. The communication network iswidely deployed to provide a variety of communication services such asvoice over internet protocol (VoIP) through IMS and packet data.

Referring to FIG. 1, the LTE system architecture includes one or moreuser equipment (UE; 10), an evolved-UMTS terrestrial radio accessnetwork (E-UTRAN) and an evolved packet core (EPC). The UE 10 refers toa communication equipment carried by a user. The UE 10 may be fixed ormobile, and may be referred to as another terminology, such as a mobilestation (MS), a user terminal (UT), a subscriber station (SS), awireless device, etc.

The E-UTRAN includes one or more evolved node-B (eNB) 20, and aplurality of UEs may be located in one cell. The eNB 20 provides an endpoint of a control plane and a user plane to the UE 10. The eNB 20 isgenerally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as a base station (BS), anaccess point, etc. One eNB 20 may be deployed per cell.

Hereinafter, a downlink (DL) denotes communication from the eNB 20 tothe UE 10, and an uplink (UL) denotes communication from the UE 10 tothe eNB 20. In the DL, a transmitter may be a part of the eNB 20, and areceiver may be a part of the UE 10. In the UL, the transmitter may be apart of the UE 10, and the receiver may be a part of the eNB 20.

The EPC includes a mobility management entity (MME) and a systemarchitecture evolution (SAE) gateway (S-GW). The MME/S-GW 30 may bepositioned at the end of the network and connected to an externalnetwork. For clarity, MME/S-GW 30 will be referred to herein simply as a“gateway,” but it is understood that this entity includes both the MMEand S-GW.

The MME provides various functions including non-access stratum (NAS)signaling to eNBs 20, NAS signaling security, access stratum (AS)security control, inter core network (CN) node signaling for mobilitybetween 3GPP access networks, idle mode UE reachability (includingcontrol and execution of paging retransmission), tracking area listmanagement (for UE in idle and active mode), packet data network (PDN)gateway (P-GW) and S-GW selection, MME selection for handovers with MMEchange, serving GPRS support node (SGSN) selection for handovers to 2Gor 3G 3GPP access networks, roaming, authentication, bearer managementfunctions including dedicated bearer establishment, support for publicwarning system (PWS) (which includes earthquake and tsunami warningsystem (ETWS) and commercial mobile alert system (CMAS)) messagetransmission. The S-GW host provides assorted functions includingper-user based packet filtering (by e.g., deep packet inspection),lawful interception, UE Internet protocol (IP) address allocation,transport level packet marking in the DL, UL and DL service levelcharging, gating and rate enforcement, DL rate enforcement based onaccess point name aggregate maximum bit rate (APN-AMBR).

Interfaces for transmitting user traffic or control traffic may be used.The UE 10 is connected to the eNB 20 via a Uu interface. The eNBs 20 areconnected to each other via an X2 interface. Neighboring eNBs may have ameshed network structure that has the X2 interface. A plurality of nodesmay be connected between the eNB 20 and the gateway 30 via an S1interface.

FIG. 2 shows a block diagram of architecture of a typical E-UTRAN and atypical EPC. Referring to FIG. 2, the eNB 20 may perform functions ofselection for gateway 30, routing toward the gateway 30 during a radioresource control (RRC) activation, scheduling and transmitting of pagingmessages, scheduling and transmitting of broadcast channel (BCH)information, dynamic allocation of resources to the UEs 10 in both ULand DL, configuration and provisioning of eNB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE_IDLE state management,ciphering of the user plane, SAE bearer control, and ciphering andintegrity protection of NAS signaling.

FIG. 3 shows a block diagram of a user plane protocol stack of an LTEsystem. FIG. 4 shows a block diagram of a control plane protocol stackof an LTE system. Layers of a radio interface protocol between the UEand the E-UTRAN may be classified into a first layer (L1), a secondlayer (L2), and a third layer (L3) based on the lower three layers ofthe open system interconnection (OSI) model that is well-known in thecommunication system.

A physical (PHY) layer belongs to the L1. The PHY layer provides ahigher layer with an information transfer service through a physicalchannel. The PHY layer is connected to a medium access control (MAC)layer, which is a higher layer of the PHY layer, through a transportchannel. A physical channel is mapped to the transport channel. Databetween the MAC layer and the PHY layer is transferred through thetransport channel. Between different PHY layers, i.e. between a PHYlayer of a transmission side and a PHY layer of a reception side, datais transferred via the physical channel.

A MAC layer, a radio link control (RLC) layer, and a packet dataconvergence protocol (PDCP) layer belong to the L2. The MAC layerprovides services to the RLC layer, which is a higher layer of the MAClayer, via a logical channel. The MAC layer provides data transferservices on logical channels. The RLC layer supports the transmission ofdata with reliability. Meanwhile, a function of the RLC layer may beimplemented with a functional block inside the MAC layer. In this case,the RLC layer may not exist. The PDCP layer provides a function ofheader compression function that reduces unnecessary control informationsuch that data being transmitted by employing IP packets, such as IPv4or IPv6, can be efficiently transmitted over a radio interface that hasa relatively small bandwidth.

A radio resource control (RRC) layer belongs to the L3. The RLC layer islocated at the lowest portion of the L3, and is only defined in thecontrol plane. The RRC layer controls logical channels, transportchannels, and physical channels in relation to the configuration,reconfiguration, and release of radio bearers (RBs). The RB signifies aservice provided the L2 for data transmission between the UE andE-UTRAN.

Referring to FIG. 3, the RLC and MAC layers (terminated in the eNB onthe network side) may perform functions such as scheduling, automaticrepeat request (ARQ), and hybrid ARQ (HARQ). The PDCP layer (terminatedin the eNB on the network side) may perform the user plane functionssuch as header compression, integrity protection, and ciphering.

Referring to FIG. 4, the RLC and MAC layers (terminated in the eNB onthe network side) may perform the same functions for the control plane.The RRC layer (terminated in the eNB on the network side) may performfunctions such as broadcasting, paging, RRC connection management, RBcontrol, mobility functions, and UE measurement reporting andcontrolling. The NAS control protocol (terminated in the MME of gatewayon the network side) may perform functions such as a SAE bearermanagement, authentication, LTE_IDLE mobility handling, pagingorigination in LTE_IDLE, and security control for the signaling betweenthe gateway and UE.

FIG. 5 shows an example of a physical channel structure. A physicalchannel transfers signaling and data between PHY layer of the UE and eNBwith a radio resource. A physical channel consists of a plurality ofsubframes in time domain and a plurality of subcarriers in frequencydomain. One subframe, which is 1 ms, consists of a plurality of symbolsin the time domain. Specific symbol(s) of the subframe, such as thefirst symbol of the subframe, may be used for a physical downlinkcontrol channel (PDCCH). The PDCCH carries dynamic allocated resources,such as a physical resource block (PRB) and modulation and coding scheme(MCS).

A DL transport channel includes a broadcast channel (BCH) used fortransmitting system information, a paging channel (PCH) used for paginga UE, a downlink shared channel (DL-SCH) used for transmitting usertraffic or control signals, a multicast channel (MCH) used for multicastor broadcast service transmission. The DL-SCH supports HARQ, dynamiclink adaptation by varying the modulation, coding and transmit power,and both dynamic and semi-static resource allocation. The DL-SCH alsomay enable broadcast in the entire cell and the use of beamforming.

FIG. 6 shows mapping between UL transport channels and UL physicalchannels. Referring to FIG. 6, an uplink shared channel (UL-SCH) may bemapped to a physical uplink shared channel (PUSCH). The UL-SCH may becharacterized by:

-   -   possibility to use beamforming;    -   support for dynamic link adaptation by varying the transmit        power and potentially modulation and coding;    -   support for HARQ;    -   support for both dynamic and semi-static resource allocation.

Further, a random access channel (RACH) may be mapped to a physicalrandom access channel (PRACH). The RACH may be characterized by:

-   -   limited control information;    -   collision risk.

The logical channels are classified into control channels fortransferring control plane information and traffic channels fortransferring user plane information, according to a type of transmittedinformation. That is, a set of logical channel types is defined fordifferent data transfer services offered by the MAC layer.

The control channels are used for transfer of control plane informationonly. The control channels provided by the MAC layer include a broadcastcontrol channel (BCCH), a paging control channel (PCCH), a commoncontrol channel (CCCH), a multicast control channel (MCCH) and adedicated control channel (DCCH). The BCCH is a downlink channel forbroadcasting system control information. The PCCH is a downlink channelthat transfers paging information and is used when the network does notknow the location cell of a UE. The CCCH is used by UEs having no RRCconnection with the network. The MCCH is a point-to-multipoint downlinkchannel used for transmitting multimedia broadcast multicast services(MBMS) control information from the network to a UE. The DCCH is apoint-to-point channel used by UEs having an RRC connection thattransmits dedicated control information between a UE and the network.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels provided by the MAC layer include a dedicatedtraffic channel (DTCH) and a multicast traffic channel (MTCH). The DTCHis a point-to-point channel, dedicated to one UE for the transfer ofuser information and can exist in both uplink and downlink. The MTCH isa point-to-multipoint downlink channel for transmitting traffic datafrom the network to the UE.

FIG. 7 shows mapping between UL logical channels and UL transportchannels. Referring to FIG. 7, the CCCH may be mapped to the UL-SCH. TheDCCH may be mapped to the UL-SCH. The DTCH may be mapped to the UL-SCH.

An RRC state indicates whether an RRC layer of the UE is logicallyconnected to an RRC layer of the E-UTRAN. The RRC state may be dividedinto two different states such as an RRC idle state (RRC_IDLE) and anRRC connected state (RRC_CONNECTED). In RRC_IDLE, the UE may receivebroadcasts of system information and paging information while the UEspecifies a discontinuous reception (DRX) configured by NAS, and the UEhas been allocated an identification (ID) which uniquely identifies theUE in a tracking area and may perform public land mobile network (PLMN)selection and cell re-selection. Also, in RRC_IDLE, no RRC context isstored in the eNB.

In RRC_CONNECTED, the UE has an E-UTRAN RRC connection and a context inthe E-UTRAN, such that transmitting and/or receiving data to/from theeNB becomes possible. Also, the UE can report channel qualityinformation and feedback information to the eNB. In RRC_CONNECTED, theE-UTRAN knows the cell to which the UE belongs. Therefore, the networkcan transmit and/or receive data to/from UE, the network can controlmobility (handover and inter-radio access technologies (RAT) cell changeorder to GSM EDGE radio access network (GERAN) with network assistedcell change (NACC)) of the UE, and the network can perform cellmeasurements for a neighboring cell.

In RRC_IDLE, the UE specifies the paging DRX cycle. Specifically, the UEmonitors a paging signal at a specific paging occasion of every UEspecific paging DRX cycle. The paging occasion is a time interval duringwhich a paging signal is transmitted. The UE has its own pagingoccasion. A paging message is transmitted over all cells belonging tothe same tracking area. If the UE moves from one tracking area (TA) toanother TA, the UE will send a tracking area update (TAU) message to thenetwork to update its location.

Proximity-based services (ProSe) are described. “ProSe” may be usedmixed with “D2D”. ProSe direct communication means a communicationbetween two or more UEs in proximity that are ProSe-enabled, by means ofuser plane transmission using E-UTRA technology via a path nottraversing any network node. ProSe-enabled UE means a UE that supportsProSe requirements and associated procedures. Unless explicitly statedotherwise, a ProSe-enabled UE refers both to a non-public safety UE anda public safety UE. ProSe-enabled public safety UE means a ProSe-enabledUE that also supports ProSe procedures and capabilities specific topublic safety. ProSe-enabled non-public safety UE means a UE thatsupports ProSe procedures and but not capabilities specific to publicsafety. ProSe direct discovery means a procedure employed by aProSe-enabled UE to discover other ProSe-enabled UEs in its vicinity byusing only the capabilities of the two UEs with 3GPP LTE rel-12technology. EPC-level ProSe discovery means a process by which the EPCdetermines the proximity of two ProSe-enabled UEs and informs them oftheir proximity. ProSe UE identity (ID) is a unique identity allocatedby evolved packet system (EPS) which identifies the ProSe enabled UE.ProSe application ID is an identity identifying application relatedinformation for the ProSe enabled UE.

Sidelink (SL) is UE to UE interface for ProSe direct communication andProSe direct discovery. The sidelink corresponds to the PC5 interface.Sidelink comprises ProSe direct discovery and ProSe direct communicationbetween UEs. Sidelink uses UL resources and physical channel structuresimilar to UL transmissions. Sidelink transmission uses the same basictransmission scheme as the UL transmission scheme. However, sidelink islimited to single cluster transmissions for all the sidelink physicalchannels. Further, sidelink uses a 1 symbol gap at the end of eachsidelink sub-frame.

FIG. 8 shows mapping between SL transport channels and SL physicalchannels. Referring to FIG. 8, a SL discovery channel (SL-DCH) may bemapped to a physical SL discovery channel (PSDCH), which carries ProSedirect discovery message from the UE. The SL-DCH is characterized by:

-   -   fixed size, pre-defined format periodic broadcast transmission;    -   support for both UE autonomous resource selection and scheduled        resource allocation by eNB;    -   collision risk due to support of UE autonomous resource        selection; no collision when UE is allocated dedicated resources        by the eNB.

Further, a SL shared channel (SL-SCH) may be mapped to a physical SLshared channel (PSSCH), which carries data from a UE for ProSe directcommunication. The SL-SCH is characterized by:

-   -   support for broadcast transmission;    -   support for both UE autonomous resource selection and scheduled        resource allocation by eNB;    -   collision risk due to support of UE autonomous resource        selection; no collision when UE is allocated dedicated resources        by the eNB;    -   support for HARQ combining, but no support for HARQ feedback;    -   support for dynamic link adaptation by varying the transmit        power, modulation and coding.

Further, a SL broadcast channel (SL-BCH) may be mapped to a physical SLbroadcast channel (PSBCH), which carries system and synchronizationrelated information transmitted from the UE. The SL-BCH is characterizedby pre-defined transport format.

A physical SL control channel (PSCCH) carries control from a UE forProSe direct communication. The PSCCH is mapped to the SL controlresources. The PSCCH indicates resource and other transmissionparameters used by a UE for PSSCH.

FIG. 9 shows mapping between SL logical channels and SL transportchannels for ProSe direct communication. Referring to FIG. 9, a SLbroadcast control channel (SBCCH) may be mapped to the SL-BCH. The SBCCHis a SL channel for broadcasting SL system information from one UE toother UE(s). This channel is used only by ProSe direct communicationcapable UEs. Further, a SL traffic channel (STCH) may be mapped to theSL-SCH. The STCH is a point-to-multipoint channel, for transfer of userinformation from one UE to other UEs. This channel is used only by ProSedirect communication capable UEs.

The buffer status reporting (BSR) procedure is used to provide theserving eNB with information about the amount of data available fortransmission in the UL buffers associated with the MAC entity. RRCcontrols BSR reporting by configuring the three timersperiodicBSR-Timer, retxBSR-Timer and logicalChannelSR-ProhibitTimer andby, for each logical channel, optionally signalling logicalChannelGroupwhich allocates the logical channel to an LCG.

BSR MAC control elements (CE) consist of either:

-   -   Short BSR and truncated BSR format: one LCG ID field and one        corresponding buffer size field; or    -   Long BSR format: four buffer size fields, corresponding to LCG        IDs #0 through #3.

The BSR formats are identified by MAC PDU subheaders with LCIDs.

The fields LCG ID and buffer size are defined as follow:

-   -   LCG ID: The logical channel group ID field identifies the group        of logical channel(s) which buffer status is being reported. The        length of the field is 2 bits;    -   Buffer size: The buffer size field identifies the total amount        of data available across all logical channels of a logical        channel group after all MAC PDUs for the transmit time interval        (TTI) have been built. The amount of data is indicated in number        of bytes. It shall include all data that is available for        transmission in the RLC layer and in the PDCP layer. The size of        the RLC and MAC headers are not considered in the buffer size        computation. The length of this field is 6 bits.

The sidelink BSR procedure is used to provide the serving eNB withinformation about the amount of SL data available for transmission inthe SL buffers of the MAC entity. RRC controls BSR reporting for thesidelink by configuring the two timers periodic-BSR-TimerSL andretx-BSR-TimerSL. Each sidelink logical channel is allocated to an LCGwith LCGID set to “11” and belongs to a ProSe destination.

Sidelink BSR MAC CE consists of:

-   -   Sidelink BSR and tuncated Sidelink BSR: one group index field,        one LCG ID field and one corresponding buffer size field per        reported target group.

The sidelink BSR is identified by MAC PDU subheaders with LCID. It has avariable size.

For each included group, the fields are defined as follow:

-   -   Group index: The group index field identifies the ProSe        destination. The length of this field is 4 bits. The value is        set to the index of the destination reported in        destinationInfoList;    -   LCG ID: The logical channel group ID field identifies the group        of logical channel(s) which buffer status is being reported. The        length of the field is 2 bits and it is set to “11”;    -   Buffer Size: The buffer size field identifies the total amount        of data available across all logical channels of a ProSe        destination after all MAC PDUs for the TTI have been built. The        amount of data is indicated in number of bytes. It shall include        all data that is available for transmission in the RLC layer and        in the PDCP layer. The size of the RLC and MAC headers are not        considered in the buffer size computation. The length of this        field is 6 bits.    -   R: Reserved bit, set to “0”.

The vehicular communication, referred to as vehicle-to-everything (V2X),contains three different types, which are vehicle-to-vehicle (V2V)communications, vehicle-to-infrastructure (V2I) communications, andvehicle-to-pedestrian (V2P) communications. These three types of V2X canuse “co-operative awareness” to provide more intelligent services forend-users. This means that transport entities, such as vehicles,roadside infrastructure, and pedestrians, can collect knowledge of theirlocal environment (e.g. information received from other vehicles orsensor equipment in proximity) to process and share that knowledge inorder to provide more intelligent services, such as cooperativecollision warning or autonomous driving.

V2X service is a type of communication service that involves atransmitting or receiving UE using V2V application via 3GPP transport.Based on the other party involved in the communication, it can befurther divided into V2V service, V2I service, V2P service. V2V serviceis a type of V2X service, where both parties of the communication areUEs using V2V application. V2I service is a type of V2X Service, whereone party is a UE and the other party is a road side unit (RSU) bothusing V2I application. The RSU is an entity supporting V2I service thatcan transmit to, and receive from a UE using V2I application. RSU isimplemented in an eNB or a stationary UE. V2P service is a type of V2Xservice, where both parties of the communication are UEs using V2Papplication.

For V2V, E-UTRAN allows such UEs that are in proximity of each other toexchange V2V-related information using E-UTRA(N) when permission,authorization and proximity criteria are fulfilled. The proximitycriteria can be configured by the mobile network operator (MNO).However, UEs supporting V2V service can exchange such information whenserved by or not served by E-UTRAN which supports V2X Service. The UEsupporting V2V applications transmits application layer information(e.g. about its location, dynamics, and attributes as part of the V2Vservice). The V2V payload must be flexible in order to accommodatedifferent information contents, and the information can be transmittedperiodically according to a configuration provided by the MNO. V2V ispredominantly broadcast-based. V2V includes the exchange of V2V-relatedapplication information between distinct UEs directly and/or, due to thelimited direct communication range of V2V, the exchange of V2V-relatedapplication information between distinct UEs via infrastructuresupporting V2X service, e.g., RSU, application server, etc.

For V2I, the UE supporting V2I applications sends application layerinformation to RSU. RSU sends application layer information to a groupof UEs or a UE supporting V2I applications. Vehicle-to-network (V2N) isalso introduced where one party is a UE and the other party is a servingentity, both supporting V2N applications and communicating with eachother via LTE network.

For V2P, E-UTRAN allows such UEs that are in proximity of each other toexchange V2P-related information using E-UTRAN when permission,authorization and proximity criteria are fulfilled. The proximitycriteria can be configured by the MNO. However, UEs supporting V2Pservice can exchange such information even when not served by E-UTRANwhich supports V2X Service. The UE supporting V2P applications transmitsapplication layer information. Such information can be broadcast by avehicle with UE supporting V2X service (e.g., warning to pedestrian),and/or by a pedestrian with UE supporting V2X service (e.g., warning tovehicle). V2P includes the exchange of V2P-related applicationinformation between distinct UEs (one for vehicle and the other forpedestrian) directly and/or, due to the limited direct communicationrange of V2P, the exchange of V2P-related application informationbetween distinct UEs via infrastructure supporting V2X service, e.g.,RSU, application server, etc.

FIG. 10 shows an example of a scenario of V2X communication. Referringto FIG. 10, vehicle 1 and vehicle 2 are communicated with each otherdirectly via PC5 interface.

FIG. 11 shows another example of a scenario of V2X communication.Referring to FIG. 11, vehicle 1 and vehicle 2 are communicated with eachother indirectly via the network. The network node may be one of an eNB,a new entity for V2X communication, a new gateway for V2X communication,a RSU, etc. The network node may not be the MME or S-GW.

FIG. 12 shows another example of a scenario of V2X communication.Referring to FIG. 12, vehicle 1 broadcasts data, and the RSU receivesthe broadcast data. The RSU and vehicle 2 are communicated with eachother indirectly via the network. The network node may be one of an eNB,a new entity for V2X communication, a new gateway for V2X communication,a RSU, etc. The network node may not be the MME or S-GW.

As described above, in 3GPP rel-12, ProSe allows a UE to discoveranother UE within an authorized range either directly or with thenetwork assistance. The discovery process is under network control, andprovides additional service related information to the discoverer UE. Inaddition, for public safety use, the UEs within the allowed range areable to directly communicate with each other using group basedcommunication. Further in 3GPP rel-13, there are plans for furtherenhancements to ProSe to support restricted discovery and targeteddiscovery, in which the user is able to control who can discoverhim/her, and to operate in a mode to only announce upon a request. Theone-to-one communication and relay support are also considered to beadded for direct communication.

All these features can find a good application in the V2X use cases.However, in 3GPP rel-12 and rel-13, the ProSe has been designed for usewith pedestrian mobility speed. It would therefore not be able to beused directly for V2X. For example, the physical channel assumptions maynot be suitable for direct discovery and communication in vehicle speed,and UE to network signaling delays would limit its usefulness for V2X.Enhancements are necessary to adapt the ProSe system to support V2X.

When the current ProSe is used for V2X communication, the followingproblems may occur.

(1) In urban area, the number of vehicles is expected to be large. Insuch dense scenario, there may be many vehicles that transmit roadsafety messages on SL, so that SL resources may be highly utilized andcollision probability will be normally high. Such problem will causeunstable intelligent transportation system (ITS) service to vehicles. Inthis sense, offloading ITS traffic from SL to another direction may bebeneficial.

(2) V2V and V2I communication may normally happen in a local area. V2Vand V2I communication may not aim at a specific user. Rather, thiscommunication may be open to all neighboring vehicles in a local area.In addition, such communication will require lower latency. Thus, fastbroadcast mechanism may be needed.

In order to solve the problem described above, according to oneembodiment of the present invention, a new type of channel ortransmission for V2X communication may be proposed. Further, accordingto another embodiment of the present invention, a new type of BSR MAC CEfor V2X communication may be proposed. Further, according to anotherembodiment of the present invention, a new type of radio networktemporary identity (RNTI) for V2X communication may be proposed.

Hereinafter, the bi-direction transmission may be included in the newkind of transmission for V2X communication according to an embodiment ofthe present invention. The bi-directional transmission may consist of ULtransmission and SL transmission. In the bi-directional transmission,traffic may be transmitted in either UL or in SL. Or, in thebi-directional transmission, transmission from a UE to another UE may beperformed in either UL or in SL. The bi-directional transmission may beperformed via the bi-directional channel. The bi-direction channel maybe included in the new kind of channel for V2X communication accordingto an embodiment of the present invention. The bi-direction channel maybe one channel which can be used as either UL channel or SL channel. Inthe bi-direction channel, traffic can be offloaded easily from SLchannel to UL channel, or vice versa. The bi-directional channel can bedivided into SL channel and UL channel at one point in L1/L2, i.e.PDCP/RLC/MAC/PHY layer.

Further, the connectionless transmission may be included in the new kindof transmission for V2X communication according to an embodiment of thepresent invention. The connectionless transmission may be a specifictype of UE-to-UE transmission via network. In connectionlesstransmission, data/message/signaling may not be routed to the S-GW, butit may be transferred from one or more UEs to one or more other UEs vianetwork. The network node may be one of an eNB, a new entity for V2Xcommunication, a new gateway for V2X communication, a RSU, etc. Thenetwork node may not be the MME or S-GW. Data/message/signaling may bespecific to V2X communication, i.e. communication between vehicles orcommunication between a vehicle and other type of device. Theconnectionless transmission may be efficient for V2X communication,because connectionless transmission would not require connectionestablishment/management between the network and vehicles.

FIG. 13 shows an example of a bi-directional channel according to anembodiment of the present invention. Referring to FIG. 13, theapplication layer may provide V2X communication. From the applicationlayer to the PDCP layer, the bi-directional channel may be configured.The bi-directional channel may be used for either UL channel or SLchannel. There may be only one PDCP entity for the bi-directionalchannel. At the PDCP layer, the bi-directional channel may be dividedinto UL channel and SL channel. Accordingly, there may be two logicalchannels, two transports channel and two physical channels for UL andSL, respectively.

FIG. 14 shows another example of a bi-directional channel according toan embodiment of the present invention. Referring to FIG. 14, theapplication layer may provide V2X communication. From the applicationlayer to the RLC layer, the bi-directional channel may be configured.The bi-directional channel may be used for either UL channel or SLchannel. There may be only one PDCP entity and one RLC entity for thebi-directional channel. At the RLC layer, the bi-directional channel maybe divided into UL channel and SL channel. Accordingly, there may be twological channels, two transports channel and two physical channels forUL and SL, respectively.

FIG. 15 shows another example of a bi-directional channel according toan embodiment of the present invention. Referring to FIG. 15, theapplication layer may provide V2X communication. From the applicationlayer to the MAC layer, the bi-directional channel may be configured.The bi-directional channel may be used for either UL channel or SLchannel. There may be only one PDCP entity, one RLC entity and one MACentity for the bi-directional channel. At the MAC layer, thebi-directional channel may be divided into UL channel and SL channel.Accordingly, there may be two transports channel and two physicalchannels for UL and SL, respectively.

FIG. 16 shows another example of a bi-directional channel according toan embodiment of the present invention. Referring to FIG. 15, theapplication layer may provide V2X communication. From the applicationlayer to the PHY layer, the bi-directional channel may be configured.The bi-directional channel may be used for either UL channel or SLchannel. There may be only one PDCP entity, one RLC entity and one MACentity for the bi-directional channel. At the PHY layer, thebi-directional channel may be divided into UL channel and SL channel.Accordingly, there may be two physical channels for UL and SL,respectively.

FIG. 17 shows a method for configuring a bi-directional channelaccording to an embodiment of the present invention.

In step S100, the UE configures the bi-directional channel which is usedfor either an UL channel or a SL channel. The bi-directional channel maybe divided into the UL channel and the SL channel at a PDCP layer. Or,the bi-directional channel is divided into the UL channel and the SLchannel at a RLC layer. Or, the bi-directional channel is divided intothe UL channel and the SL channel at a MAC layer. In this case, thebi-directional channel may correspond to a specific type of logicalchannel. Or, the bi-directional channel may be divided into the ULchannel and the SL channel at a physical layer. In this case, thebi-directional channel may correspond to a specific type of transportchannel.

In step S110, the UE transmits data via at least one of the UL channelor the SL channel. The UE may be a vehicle. The data may be specific tovehicular communication between vehicles or between a vehicle and othertype of device. The other type of device may be one of an eNB, a newentity for the vehicular communication, a new gateway for the vehicularcommunication, or a RSU. The data may be transmitted via the UL channelbased on a UL grant. The data may be transmitted via the SL channelbased on a SL grant. The data may be transmitted with a digitalsignature or encryption.

FIG. 18 shows a method for transmitting a buffer status report for abi-directional transmission according to an embodiment of the presentinvention.

In step S200, the UE triggers a buffer status report for abi-directional transmission. The buffer status report for thebi-directional transmission may inform the network about amount of dataavailable for the bi-directional transmission. The buffer status reportfor the bi-directional transmission may be transmitted via a newlydefined BSR MAC CE for the bi-directional transmission. The UE may be avehicle. The bi-directional transmission may consist of an ULtransmission and a SL transmission. The bi-directional transmission maybe specific to vehicular communication between vehicles or between avehicle and other type of device.

In step S200, the UE transmits the buffer status report for thebi-directional transmission or a scheduling request for thebi-directional transmission to a network. The scheduling request for thebi-directional transmission may indicate a specific type of logicalchannel for the bi-directional transmission. The scheduling request forthe bi-directional transmission may be transmitted via a specific codepoint on a PUCCH. Or, the scheduling request for the bi-directionaltransmission is transmitted via a specific code point on a new uplinkchannel. Or, the scheduling request for the bi-directional transmissionis transmitted via a specific random access preamble ID dedicated to thescheduling request for the bi-directional transmission. The networkcorresponds to one of an eNB, a new entity for the vehicularcommunication, a new gateway for the vehicular communication, or a RSU.The UE may receive a UL grant after transmitting the scheduling requestto the network. The UE may receive either a UL grant or a SL grant aftertransmitting the buffer status report to the network.

FIG. 19 shows a method for transmitting data for a bi-directionaltransmission according to an embodiment of the present invention.

In step S300, the UE receives a grant including a RNTI for thebi-directional transmission from a network. The grant may be receivedvia a PDCCH or enhanced PDCCH (ePDCCH). The grant may be one of an ULgrant or a SL grant. Further, the UE may transmit a buffer status reportfor the bi-directional transmission or a scheduling request for thebi-directional transmission to a network, before receiving the grant.The network may correspond to one of an eNB, a new entity for thevehicular communication, a new gateway for the vehicular communication,or a RSU. The UE may be a vehicle.

Upon detecting the RNTI for the bi-directional transmission, in stepS310, the UE transmit data via at least one of an UL channel or a SLchannel. The data may be specific to vehicular communication betweenvehicles or between a vehicle and other type of device. The other typeof device may be one of an eNB, a new entity for the vehicularcommunication, a new gateway for the vehicular communication, or a RSU.The data may be transmitted with a digital signature or encryption.

Based on the above description according to embodiments of the presentinvention, various methods for performing bi-directional transmissionaccording to embodiments of the present invention are described below.

Hereinafter, the bi-directional transmission may consist of ULtransmission and SL transmission. In the bi-directional transmission,traffic may be transmitted in either UL or in SL. Or, in thebi-directional transmission, transmission from a UE to another UE may beperformed in either UL or in SL. The bi-directional transmission may beperformed via the bi-directional channel described by referring to FIG.13 to FIG. 16. Further, the connectionless transmission may be aspecific type of UE-to-UE transmission via network. In connectionlesstransmission, data/message/signaling may not be routed to the S-GW, butit may be transferred from one or more UEs to one or more other UEs vianetwork. The network or network node may be one of an eNB, a new entityfor V2X communication, a new gateway for V2X communication, a RSU, etc.The network node may not be the MME or S-GW. The data/message/signalingmay be specific to V2X communication, i.e. communication betweenvehicles or communication between a vehicle and other type of device.

FIG. 20 shows a method for performing bi-directional transmissionaccording to an embodiment of the present invention. According to thisembodiment, transmission direction between UL and SL may be selectedunder a resource grant. According to this embodiment, whendata/message/signaling is available for bi-directional transmission, theUE may transmit a scheduling request indicating bi-directionaltransmission or a buffer status report indicating bi-directiontransmission, in order to receive a grant for UL resource or SLresource. Then, the UE may perform UL transmission or SL transmissionbased on the received grant.

In step S400, the UE detects available data/message/signaling forbi-directional transmission. There may be a specific type of logicalchannels for bi-directional transmission. In this case, the UE maydetect available data for this type of logical channels. Alternatively,there may be a specific type of bi-directional channel forbi-directional transmission by referring to FIG. 13 to FIG. 16.

Upon detecting or upon triggering of a buffer status report forbi-directional transmission, in step S410, the UE may transmit ascheduling request. The scheduling request may indicate bi-directionaltransmission or the specific type of bi-directional channel. Thescheduling request may be indicated to the network by a specific codepoint in PUCCH or a new UL channel. Or, the scheduling request may beindicated to the network by a specific random access preamble ID.

In step S420, the UE may receive UL grant after transmitting thescheduling request.

In step S430, the UE transmits a buffer status report to the network.The buffer status report may inform the network about the amount of dataavailable for bi-directional transmission. The buffer status report maybe one of normal BSR MAC CE, ProSe BSR MAC CE, and a new type of BSR MACCE for bi-directional transmission which indicates bi-directionaltransmission.

In step S440, the UE receives either UL grant or SL grant onPDCCH/ePDCCH. The grant may be received on PDCCH/ePDCCH which includes aspecific RNTI specific to bi-directional transmission. Or, the grant mayinclude a specific RNTI specific to the connectionless transmission(CL-RNTI).

In step S450, depending on the received grant, the UE may perform eitherUL transmission or SL transmission. If the SL grant is received, the UEmay perform SL transmission to transmit the data/message/signaling. Ifthe UL grant is received, the UE may perform UL transmission to transmitthe data/message/signaling. The data/message/signaling may betransmitted with a digital signature or encryption. The receiving sidemay reconstruct the data/message/signaling with the digital signature ordecrypt the data/message/signaling.

FIG. 21 shows a method for performing bi-directional transmissionaccording to another embodiment of the present invention. According tothis embodiment, bi-directional transmission and/or connectionlesstransmission may be performed based on a random access. According tothis embodiment, when data/message/signaling is available forbi-directional transmission and/or connectionless transmission, the UEmay transmit a random access preamble dedicated to bi-directionaltransmission and/or connectionless transmission. Upon receiving therandom access response, the UE may perform UL transmission and/or SLtransmission indicating bi-directional transmission and/orconnectionless transmission. The UE may be in RRC_IDLE or RRC_CONNECTED.

In step S500, the UE receives control information on bi-directionaltransmission and/or connectionless transmission at a cell. The controlinformation may indicate that the cell supports bi-directionaltransmission and/or connectionless transmission. The control informationmay indicate transmission direction, if this transmission corresponds tobi-directional transmission by which the UE can transmit a packet in ULor in SL. The control information may include UL resource pool and/or SLresource pool, used for bi-directional transmission and/orconnectionless transmission. The control information may include a setof random access preamble IDs and time resource for this set ofpreambles.

In step S510, the UE detects data available for bi-directionaltransmission and/or connectionless transmission. There may be a specifictype of logical channels for bi-directional transmission. Alternatively,there may be a specific type of bi-directional channel forbi-directional transmission by referring to FIG. 13 to FIG. 16. Theremay be a specific logical/transport channel for connectionlesstransmission, which is called connectionless channel.

In step S520, the UE transmits a random access preamble ID dedicated tobi-directional transmission and/or connectionless transmission.

In step S530, the UE receives a random access response including ULgrant or SL grant. The grant may be received on PDCCH/ePDCCH whichincludes a specific RNTI specific to bi-directional transmission. Or,the grant may include a CL-RNTI.

In step S540, upon receiving the SL grant, the UE may perform SLtransmission indicating bi-directional transmission and/or SLconnectionless transmission to transmit the data/message/signaling. Instep S550, upon receiving the uplink grant, the UE may perform ULtransmission indicating bi-directional transmission and/or ULconnectionless transmission to transmit the data/message/signaling. Thedata/message/signaling may be transmitted with a digital signature orencryption.

Upon receiving data/message/signaling by UL connectionless transmission,in step S560, a network node (e.g. eNB) determines whether or not torelay the received data/message/signaling to one or more other UE(s) inthe cell or in a specific area. The network node may receive similardata/message/signaling from many UEs in the cell from the same ULconnectionless channel. The network node may detect duplicateddata/message/signaling, so that the network node may not relay all thereceived ones. Rather, the network node may select one or some of thereceived ones for relaying. Alternatively, the network node mayre-construct a new data/message/signaling based on the received ones,and transmit the re-constructed data/message/signaling to one or moreother UEs in the cell or in a specific area.

In step S570, the network node may perform DL transmission either forrelaying the received data/message/signaling or for transmitting newdata/message/signaling re-constructed based on the receiveddata/message/signaling.

FIG. 22 shows a method for performing bi-directional transmissionaccording to another embodiment of the present invention. According tothis embodiment, bi-directional transmission and/or connectionlesstransmission may be performed. According to this embodiment, whendata/message/signaling is available for bi-directional transmissionand/or connectionless transmission, the UE may perform bi-directionaltransmission and/or connectionless transmission of MAC PDU indicatingbi-directional transmission and/or connectionless transmission, possiblyby selecting a radio resource from a set of contention based resourceswhich can be shared by UEs performing bi-directional transmission and/orconnectionless transmission. The UE may transmit a scheduling request onPUCCH which is dedicated to bi-directional transmission and/orconnectionless transmission, before bi-directional transmission and/orconnectionless transmission. Upon receiving resource grant forbi-directional transmission and/or connectionless transmission, the UEmay perform bi-directional transmission and/or connectionlesstransmission based on the received resource grant. The UE may be inRRC_CONNECTED.

In step S600, the UE receives control information on bi-directionaltransmission and/or connectionless transmission at a cell. The controlinformation may indicate that the cell supports bi-directionaltransmission and/or connectionless transmission. The control informationmay indicate transmission direction, if this transmission corresponds tobi-directional transmission by which the UE can transmit a packet in ULor in SL. The control information may include UL resource pool and/or SLresource pool, used for bi-directional transmission and/orconnectionless transmission. The control information may include a setof contention based resources in time and frequency.

In step S610, the UE detects data available for bi-directionaltransmission and/or connectionless transmission. There may be a specifictype of logical channels for bi-directional transmission. Alternatively,there may be a specific type of bi-directional channel forbi-directional transmission by referring to FIG. 13 to FIG. 16. Theremay be a specific logical/transport channel for connectionlesstransmission, which is called connectionless channel.

In step S620, the UE may optionally transmit a scheduling request onPUCCH which is dedicated to bi-directional transmission and/orconnectionless transmission.

In step S630, the UE may optionally receive UL grant or SL grant forbi-directional transmission and/or connectionless transmission. Thegrant may be received on PDCCH/ePDCCH which includes a specific RNTIspecific to bi-directional transmission. Or, the grant may include aCL-RNTI.

In step S640, upon receiving the SL grant, the UE may select a radioresource from the set of contention based resources and performs SLtransmission of MAC PDU indicating bi-directional transmission and/or SLconnectionless transmission by using the selected resource in order totransmit the data/message/signaling. The LCID field in the header of theMAC PDU may include a specific value indicating bi-directionaltransmission and/or SL connectionless transmission. In step S650, uponreceiving the UL grant, the UE may select a radio resource from the setof contention based resources and performs UL transmission of MAC PDUindicating bi-directional transmission and/or UL connectionlesstransmission by using the selected resource in order to transmit thedata/message/signaling. The LCID field in the header of the MAC PDU mayinclude a specific value indicating bi-directional transmission and/orUL connectionless transmission. The data/message/signaling may betransmitted with a digital signature or encryption.

Upon receiving data/message/signaling by UL connectionless transmission,in step S660, a network node (e.g. eNB) determines whether or not torelay the received data/message/signaling to one or more other UE(s) inthe cell or in a specific area. The network node may receive similardata/message/signaling from many UEs in the cell from the same ULconnectionless channel. The network node may detect duplicateddata/message/signaling, so that the network node may not relay all thereceived ones. Rather, the network node may select one or some of thereceived ones for relaying. Alternatively, the network node mayre-construct a new data/message/signaling based on the received ones,and transmit the re-constructed data/message/signaling to one or moreother UEs in the cell or in a specific area.

In step S670, the network node may perform DL transmission either forrelaying the received data/message/signaling or for transmitting newdata/message/signaling re-constructed based on the receiveddata/message/signaling.

FIG. 23 shows a method for performing bi-directional transmissionaccording to another embodiment of the present invention. According tothis embodiment, connectionless bi-directional transmission on SL-SCH orSL-DCH may be performed. According to this embodiment, whendata/message/signaling is available for connectionless bi-directionaltransmission, the UE may transmit UL data on a SL channel such as SL-SCHor SL-DCH under network control.

In step S700, the UE receives control information on connectionlessbi-directional transmission at a cell. The control information mayindicate that the cell supports connectionless transmission. The controlinformation may indicate transmission direction, if this transmissioncorresponds to bi-directional transmission by which the UE can transmita packet in UL or in SL. The control information may include UL resourcepool for connectionless transmission. The control information mayinclude a set of SL TX resources which can be also used for ULtransmission towards the network.

In step S710, the UE detects data available for connectionlessbi-directional transmission. There may be a specific type oflogical/transport channels for connectionless bi-directionaltransmission, which is called connectionless channel. Alternatively,there may be a specific type of bi-directional channel for ULconnectionless bi-directional transmission by referring to FIG. 13 toFIG. 16.

In step S720, the UE may transmit a scheduling request on PUCCH which isdedicated to connectionless bi-directional transmission. The UE mayfurther transmit a buffer status report for connectionlessbi-directional transmission.

In step S730, the UE may receive SL grant or SL TX resources for ULconnectionless bi-directional transmission towards the network (possiblyas well as SL transmission towards another UE(s)). The SL grant or theSL TX resource may include resources for transmission of schedulingassignment and SL-SCH. Or, the SL grant or the SL TX resource mayinclude resources for transmission of SL-DCH. Or, the SL grant or the SLTX resource may include resources for transmission of SL-BCH. The SLgrant may be received on PDCCH/ePDCCH which includes a specific RNTIspecific to bi-directional transmission. Or, the grant may include aCL-RNTI.

Upon receiving the SL grant or the SL TX resource, in step S740, the UEmay perform transmission of scheduling assignment that schedulestransmission of the data/message/signaling towards the network. AnotherUE may also receive this scheduling assignment. The LCID field in theheader of the MAC PDU may include a specific value indicating ULconnectionless bi-directional transmission.

Upon receiving the SL grant or the SL TX resource, in step S750, the UEmay perform UL transmission of MAC PDU via one of SL channels (such asSL-SCH, SL-DCH, SL-BCH) based on the SA in order to transmit thedata/message/signaling to the network. Another UE may also receive thisMAC PDU on the SL channel. The LCID field in the header of the MAC PDUmay include a specific value indicating UL connectionless bi-directionaltransmission. The data/message/signaling may be transmitted with adigital signature or encryption.

Upon receiving data/message/signaling by UL connectionless transmission,in step S760, a network node (e.g. eNB) determines whether or not torelay the received data/message/signaling to one or more other UE(s) inthe cell or in a specific area. The network node may receive similardata/message/signaling from many UEs in the cell from the same ULconnectionless channel. The network node may detect duplicateddata/message/signaling, so that the network node may not relay all thereceived ones. Rather, the network node may select one or some of thereceived ones for relaying. Alternatively, the network node mayre-construct a new data/message/signaling based on the received ones,and transmit the re-constructed data/message/signaling to one or moreother UEs in the cell or in a specific area.

In step S770, the network node may perform DL transmission either forrelaying the received data/message/signaling or for transmitting newdata/message/signaling re-constructed based on the receiveddata/message/signaling.

FIG. 24 shows a wireless communication system to implement an embodimentof the present invention.

A network node 800 may include a processor 810, a memory 820 and atransceiver 830. The network node 800 may be one of an eNB, a new entityfor V2X communication, a new gateway for V2X communication, a RSU, etc.The processor 810 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 810. Thememory 820 is operatively coupled with the processor 810 and stores avariety of information to operate the processor 810. The transceiver 830is operatively coupled with the processor 810, and transmits and/orreceives a radio signal.

A UE 900 may include a processor 910, a memory 920 and a transceiver930. The UE 900 may be a vehicle. The processor 910 may be configured toimplement proposed functions, procedures and/or methods described inthis description. Layers of the radio interface protocol may beimplemented in the processor 910. The memory 920 is operatively coupledwith the processor 910 and stores a variety of information to operatethe processor 910. The transceiver 930 is operatively coupled with theprocessor 910, and transmits and/or receives a radio signal.

The processors 810, 910 may include application-specific integratedcircuit (ASIC), other chipset, logic circuit and/or data processingdevice. The memories 820, 920 may include read-only memory (ROM), randomaccess memory (RAM), flash memory, memory card, storage medium and/orother storage device. The transceivers 830, 930 may include basebandcircuitry to process radio frequency signals. When the embodiments areimplemented in software, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The modules can be stored inmemories 820, 920 and executed by processors 810, 910. The memories 820,920 can be implemented within the processors 810, 910 or external to theprocessors 810, 910 in which case those can be communicatively coupledto the processors 810, 910 via various means as is known in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

What is claimed is:
 1. A method for transmitting, by a user equipment(UE), a buffer status report for a bi-directional transmission in awireless communication system, the method comprising: triggering abuffer status report for the bi-directional transmission; andtransmitting the buffer status report for the bi-directionaltransmission or a scheduling request for the bi-directional transmissionto a network.
 2. The method of claim 1, wherein the buffer status reportfor the bi-directional transmission informs the network about amount ofdata available for the bi-directional transmission.
 3. The method ofclaim 1, wherein the buffer status report for the bi-directionaltransmission is transmitted via a newly defined BSR media access control(MAC) control element (CE) for the bi-directional transmission.
 4. Themethod of claim 1, wherein the scheduling request for the bi-directionaltransmission indicates a specific type of logical channel for thebi-directional transmission.
 5. The method of claim 1, wherein thescheduling request for the bi-directional transmission is transmittedvia a specific code point on a physical uplink control channel (PUCCH).6. The method of claim 1, wherein the scheduling request for thebi-directional transmission is transmitted via a specific code point ona new uplink channel.
 7. The method of claim 1, wherein the schedulingrequest for the bi-directional transmission is transmitted via aspecific random access preamble identifier (ID) dedicated to thescheduling request for the bi-directional transmission.
 8. The method ofclaim 1, wherein the UE is a vehicle.
 9. The method of claim 1, whereinthe bi-directional transmission consists of an uplink (UL) transmissionand a sidelink (SL) transmission.
 10. The method of claim 1, wherein thebi-directional transmission is specific to vehicular communicationbetween vehicles or between a vehicle and other type of device.
 11. Themethod of claim 1, wherein the network corresponds to one of an evolvedNodeB (eNB), a new entity for the vehicular communication, a new gatewayfor the vehicular communication, or a road side unit (RSU).
 12. Themethod of claim 1, further comprising receiving a UL grant aftertransmitting the scheduling request to the network.
 13. The method ofclaim 1, further comprising receiving either a UL grant or a SL grantafter transmitting the buffer status report to the network.
 14. A userequipment (UE) comprising: a memory; a transceiver; and a processorcoupled to the memory and the transceiver, and configured to: trigger abuffer status report for a bi-directional transmission, and control thetransceiver to transmit the buffer status report for the bi-directionaltransmission or a scheduling request for the bi-directional transmissionto a network.